This project focuses on the mechanisms by which cadherins, integrins and the cytoskeleton cooperate to regulate proliferation in endothelial and smooth muscle (vascular) cells. Aberrant proliferation of vascular cells plays a major role in the pathophysiology of atherosclerosis and arteriosclerosis, and likely is triggered by changes in the local tissue microstructure that alter cell-cell and cell-extracellular matrix interactions. Understanding the molecular basis for how cues within the tissue microenvironment are integrated within cells to regulate proliferation is hence a priority in the development of rational strategies to interrupt progression of vascular disease. It is proposed that Rho-mediated tension generated in the actin cytoskeleton couples signals from cadherins and integrins in an integrated mechanochemical signaling system that regulates proliferation of both endothelial and smooth muscle cells. During the past grant period, the investigator developed a micropatterning tool to independently manipulate cell-cell contact and cell-substrate adhesion, and combined this tool with molecular approaches to demonstrate that cadherin-mediated cell-cell contact initiates a stimulatory signal for proliferation. This novel cadherin-mediated proliferative signal requires Rho-driven changes in cytoskeletal tension, and is associated with increased focal adhesion signaling. Specific Aim 1 will be to further characterize the mechanism by which cadherin engagement triggers proliferative signaling. In particular, the investigator will examine whether cadherin engagement is necessary or also sufficient for RhoA activity and proliferation. Specific Aim 2 will be to investigate the mechanism by which cadherins activate RhoA. We will examine the role of the cadherin-associated scaffolding protein, p120-catenin, in the induction of RhoA activity and cytoskeletal tension by cadherin engagement. Specific Aim 3 will be to examine the role of focal adhesions and FAK in the transduction of cadherin-induced proliferative signals. Specific Aim 4 will be to explore the involvement of vascular cadherins, RhoA, cytoskeletal tension, and FAK in atherosclerotic lesions. This project will lead to an integrated molecular understanding of how endothelial and smooth muscle cells coordinate signals from cadherins, integrins, and cytoskeletal tension into a proliferative response, and may suggest new therapeutic strategies to interrupt the progression of atherosclerosis and arteriosclerosis.